The Core Mass Spectrometry has continued to provide analytical support for the individual program projects for almost 10 years. Mass spectrometry has been successful used in various studies and has proven to be a valuable and adequate technique for the type of studies proposed in this application. Mass spectrometry is an important aspect of the ongoing research and will be utilized by all program project investigators essentially for two general purposes: (a) quantitative analyses of PO450- derived metabolites of arachidonic acid and carbon monoxide, and (b) qualitative (structural) analyses. We have developed in our laboratory quantitative assays based on isotopic dilution GC/MS for CO, 20-HETE and other subterminal HETEs, isomers of epoxyeicosatrienoic acids (EETs) and also for omega-hydroxylated prostaglandins. Because all samples from individual investigators are analyzed by this dedicated core facility with long experience in mass spectrometry, the quantitative data are obtained in a uniform manner, with high quality control and at optimal cost. Samples are analyzed at the same conditions through the study period. Additionally, we have developed a system for sample handling and analysis that utilizes the instrument and staff time efficiently and reduces operational costs while delivering accurate results in a timely manner. Utilization of various aspects of mass spectrometry is an important feature of this program project proposal. This stems from the recognition that mass spectrometric analysis provide adequate sensitivity, specificity, and selectively required for detection and characterization of sub-picomolar quantities of eicosanoids typically found in the biological material. In particular, metabolites or arachidonic acid formed via cytochrome P450 pathway can only e measured accurately and precisely using GC/MS at subpicomolar levels since no other technique of comparable sensitivity and specificity is currently available for their quantitation. A novel aspect of the Core function is the development of an accurate method for quantitative analysis of CO originating from biological material. Using these methodologies, the Core will support Program Project Investigators in their efforts to answer fundamental questions regarding the role of eicosanoids in the mechanisms of hypertension.